An example of the conventional method for allocating wireless resource to physical control channels is described below using PDCCH Physical Downlink Control Channel) as an example. PDCCH is a physical control channel used in LTE (Long Term Evolution), i.e., the communication method being considered in 3GPP (3rd Generation Partnership Project).
FIG. 1 is a view illustrating the configuration of a conventional communication apparatus. Reference numeral 200 denotes a base station apparatus, reference numeral 201 denotes an information assembling unit, reference numeral 202 denotes an encoding unit, and reference numeral 203 denotes a modulation unit. Reference numeral 204 denotes an amplifier, and reference numeral 205 denotes an antenna.
Reference numeral 211 denotes a DCI (Downlink Control Information) assembling unit, reference numeral 212 denotes a PDCCH signal assembling unit, reference numeral 213 denotes a scrambler, reference numeral 214 denotes a quadrature modulator, and reference numeral 215 denotes an interleaver. The quadrature modulator 214 is a phase shift modulator or a quadrature amplitude modulator, for example. In the description that follows, the term “quadrature modulation” includes both phase shift modulation and quadrature amplitude modulation.
Reference numeral 216 denotes a cyclic shift unit, reference numeral 217 denotes a resource element (RE) mapping unit, reference numeral 218 denotes an inverse Fourier transformation unit (IFFT) and reference numeral 219 denotes a cyclic prefix (CP) insertion unit.
The base station apparatus 200 includes the information assembling unit 201, the encoding unit 202, the modulation unit 203, the amplifier 204, and the antenna 205. The information assembling unit 201 includes the DCI assembling unit 211.
To the DCI assembling unit 211, DCI payload including Downlink Control Information (DCI) and DCI format identifying information are inputted. DCI payload has been generated in a plurality of different formats, and a format of each DCI payload is identified by using the DCI format identifying information. The DCI assembling unit 211 assembles DCI signal by combining DCI payloads in accordance with the DCI format identifying information for each DCI payload.
FIG. 2A and FIG. 2B respectively depict DCI payloads that are inputted to the DCI assembling unit 211. Reference numerals 220 to 222 denote 3 different DCI payloads each generated in a first DCI format, and reference numerals 223 to 225 denote DCI payloads each generated in a second DCI format. FIG. 2C depicts DCI signal that is assembled by combining the DCI payloads 220 to 222 by the DCI assembling unit 211. FIG. 2D depicts DCI signal that is assembled by combining the DCI payloads 223 to 225 by the DCI assembling unit 211.
Referring to FIG. 1, the DCI assembling unit 211 outputs the generated DCI signal to the encoding unit 202. The encoding unit 202 encodes the DCI signal in accordance with PDCCH format information. FIG. 2E depicts the encoded DCI signal that has been generated by encoding of the DCI signal of FIG. 2C by the encoding unit 202. FIG. 2F depicts the encoded DCI signal that has been generated by encoding of the DCI signal of FIG. 2D by the encoding unit 202.
The PDCCH format information designates the data length of data to which the DCI signal is to be encoded. CCE (Control Channel Element) is used as unit of data length for the PDCCH format information to designate data length after encoding. It is assumed that DCI signals after encoding as depicted in FIG. 2E and FIG. 2F have data length corresponding to 1 CCE and 2 CCE, respectively.
1 CCE corresponds to the number of symbols transmitted by 9 Resource Element Group (REG). In the description that follows, Resource Element Group may be referred to as “REG”.
REG is unit of wireless resource in mapping control information to wireless resource, and 1 REG includes 4 Resource Elements (RE). 1 Resource Element is a wireless resource that uses 1 subcarrier in 1 Basic Time Unit.
Referring to FIG. 1, the DCI signal that has been encoded by the encoding unit 202 is modulated to OFDM signal by the modulation unit 203. The amplifier 204 amplifies the OFDM signal, and the amplified OFDM signal is transmitted from the antenna 205.
The modulation unit 203 includes the PDCCH signal assembling unit 212, the scrambler 213, the quadrature modulator 214, the interleaver 215, and the cyclic shift unit 216. The modulation unit 203 further includes the resource element mapping unit 217, the inverse Fourier transformation unit 218, and the cyclic prefix insertion unit 219.
The PDCCH signal assembling unit 212 combines the encoded DCI signals encoded by the encoding unit 202. For convenience of simple description of the invention, data that are generated by the PDCCH signal assembling unit 212 by combining the encoded DCI signals will be hereinafter referred to as “PDCCH data”, and the DCI signal encoded by the encoding unit 202 will be referred to as “coded data”.
The PDCCH signal assembling unit 212 determines the starting position for storing the coded data in the PDCCH data by the terminal identifier of the destination mobile station apparatus to which the coded data are to be transmitted. As the starting position for storing the coded data in the PDCCH data, a position shifted by 1 CCE has been designated in advance. In accordance with designation of CCE number that determines the starting position corresponding to the terminal identifier of the destination mobile station apparatus, the PDCCH signal assembling unit 212 stores the coded data to a position corresponding to the designated CCE number.
FIG. 2G illustrates an example of PDCCH data generated by the PDCCH signal assembling unit 212. The number in the parenthesis below the rectangle depicting PDCCH data is CCE number that designates the starting position for storing the coded data in the PDCCH data. In the example illustrated in FIG. 2G, the coded data 228 depicted in FIG. 2E are stored in a region of 1 CCE in length starting from the CCE number 7, and the coded data 227 depicted in FIG. 2F are stored in a region of 2 CCE in length starting from the CCE number 3.
The PDCCH signal assembling unit 212 inserts NIL data into a region of PDCCH data where there is no coded data to be stored so as to indicate that the region is empty. In the example depicted in FIG. 2G, NIL data are inserted into the regions of CCE number 1 and 2. In REG where NIL data are mapped, no valid data are transmitted.
Referring to FIG. 1, the scrambler 213 scrambles the PDCCH data in a scramble sequence proper to the base station 200. The quadrature modulator 214 generates a quadrature modulated signal by quadrature modulation of the scrambled PDCCH data.
The interleaver 215 performs an interleave processing on the quadrature modulated signal that is outputted from the quadrature modulator 214 in unit of symbols transmitted in 1 REG. The cyclic shift unit 216 imparts a cyclic shift to the quadrature modulated signal after interleave processing.
FIG. 3A depicts the PDCCH data depicted in FIG. 2G after processing by the scrambler 213, the quadrature modulator 214, the interleaver 215 and the cyclic shift unit 216. FIG. 3A indicates that data representing the information included in the coded data 228 depicted in FIG. 2G are stored in the portion denoted by reference numeral 230, and data representing the information included in the coded data 227 are stored in the portion denoted by reference numeral 231. NIL data are stored in the portions denoted by reference numerals 232 and 233.
Referring to FIG. 1, the resource element mapping unit 217 maps the data of FIG. 3A having cyclic shift imparted thereto to various resource elements. The number of OFDM (Orthogonal Frequency Division Multiplexing) symbols is designated by the value of CFI (control format indicator) transmitted by PCFICH (Physical Control Format Indicator Channel). FIG. 3B illustrates a state in which CFI is 3 and data in FIG. 3A are mapped to various resource elements by the resource element mapping unit 217. As illustrated in FIG. 3B, NIL data stored in data of FIG. 3A are mapped to several resource elements.
Referring to FIG. 1, the resource element mapping unit 217 maps control information, and at the same time maps main signal to resource elements. Description of the processing of the main signal is omitted.
The inverse Fourier transformation unit 218 generates OFDM signal by inverse Fourier transformation of the symbol that is mapped to each resource element. The cyclic prefix insertion unit 219 inserts a cyclic prefix to the OFDM signal.
As has been described above, the coded data after being encoded by the encoding unit 202 have a length that is an integral multiple of CCE, where 1 CCE includes 9 REG. Thus, NIL data are stored in the remainder obtained by dividing a total number of REG allocated for mapping of PDCCH by 9.
For example, a case where PDCCH is mapped only to a first OFDM symbol will be illustrated below. A number of subcarriers for 1 OFDM symbol is assumed to be 300, and PCFICH is assumed to use 4 REG, and PHICH (Physical Hybrid ARQ Indicator Channel) is assumed to use 3 REG. PHICH is a channel for transmitting retransmission control signal of uplink hybrid ARQ (Automatic repeat-request).
Since, in the first OFDM symbol, 6 subcarriers are allocated to 1 REG, there are 50 REGs in the first OFDM symbol. Therefore, number of REGs that can be allocated to PDCCH is 50−(4+3)=43. Since the remainder of 43 divided by 9 is 7, no control information is allocated to the 7 REGs, and NIL data are inserted to the 7 REGs.
The PDCCH signal assembling unit 212 stores coded data in accordance with CCE number defined by the terminal identifier of the destination mobile station apparatus. Thus, a gap may be produced between coded data stored in PDCCH data, and NIL data are also inserted in such a gap.
Since no valid data are transmitted in REG having NIL data mapped thereto, the larger the number of REG having NIL data mapped thereto, the lower is the utilization efficiency of wireless resource.
A wireless terminal apparatus has been proposed in which, in downlink from a wireless base station apparatus to wireless terminal apparatuses, PCFICH is arranged from starting subcarrier of the first OFDM symbol in a sub-frame, and ACK/NACK (ACK/NACK for UL) signal for uplink from wireless terminal apparatuses to the wireless base station apparatus is blocked and multiplexed in frequency domain so that ACK/NACK signal and PDCCH are multiplexed using frequency division multiplexing and time division multiplexing.
User equipment for wireless communication with the base station apparatus in a mobile communication system has also been proposed. Such a user equipment includes a receiver unit for receiving a first shared channel in a downlink, a transmission unit for transmitting arrival acknowledgement information and a second shared channel in an uplink. In uplink signal that requires no arrival acknowledgement information, mapping of the second shared channel to the bit region for arrival acknowledgement information is forbidden.